Tryp Operon Flashcards
What is the Trp operon?
Is turned on when tryptophan isnt available from the environment
Enzymes trp B and A, encode what in trp operon?
tryptophan synthetase
The trp operon regulated by what?
Negative regulation (involves a repressor)
Attenuation (regulartion after transcriptions inititiated)
What is the TrpR repressor?
it’s the repressor in the Trp operon
When tryphtophan binds to the TrpR what happens?
the repressor binds to the operator (TrpO) and inhibit transcription of the operon
When does the repressor bind to the operator in the Trp operon?
When tryp is present in the environment
In the absence of tryptophan what happens to the tryp operon?
the repressor can’t bind so operon is on so tryptophan is synthesized
What is attentuation in the tryp operon?
is a decrease in mRNA production by a factor of 10 when tryptophan is abundant
When does attenuation occur?
after initiation of transcription
What is the leader sequence? How long is it?
In tryp operon, is 162 bp long
What is encoded in the leader sequence?
two tryps- TrpL
attenuator region
two other regions
What structures do mRNA leader sequences form?
stem-loop structures, which only have two regions form this at once
How does the tryp operon perform when there’s a high tryp level?
the leader peptide is translated by ribosome, no loop forms betwene regions 2 and 3, however 3 and 4 form a loop which causes transcription to stop after 140 bases
How does the tryp operon perform when there’s a low tryp level?
the ribosome stalls at the leader peptide cause there’s not enough tryp to make the peptide, regions 2 and 3 loop so RNA polymerase can make mrna and transcribe at the end of the leader sequence
What is factor independent termination in the Trp operon?
the 3-4 stem loop is followed by a string of U’s when transcribed, which cause termination of rna polymerase.
